1. Technical Field of the Invention
The present invention relates to a heating control method of a heat development recording device for developing under heating a photosensitive and heat-sensitive recording material having a latent image formed therein while conveying it and to a heat development recording device.
2. Description of the Related Art
In recent years, in the medical field, a reduction of the quantity of treated wastewater is eagerly demanded from the viewpoints of environmental conservation and space saving. Thus, it is considered that technologies regarding photosensitive heat development photographic materials useful for medical diagnosis and photographic technology, which can be efficiently exposed by a laser image setter or a laser imager and are able to form clear black images having a high dissolution and sharpness, are required. According to these photosensitive heat development photographic materials, it is possible to supply a heat development processing system which is free from use of solution based treating chemicals, is simpler and does not affect consideration for the environment.
For these reasons, in recent years, heat development recording devices by a dry system without need for carrying out wet processing are watched. In these heat development recording devices, films of photosensitive and heat-sensitive recording materials (photosensitive heat-sensitive recording materials) or heat development photosensitive materials are used. Such materials will be hereinafter referred to as “heat development recording material” (sometimes referred to as “photosensitive material”). In the heat development recording device by a dry system, laser light is irradiated (scanned) on a heat development recording material to form a latent image in an exposure section; the heat development recording material is then brought into contact with heating means to achieve heat development in a heat development section; and after cooling, the heat development recording material having an image formed therein is discharged from the device. Such a dry system is able to overcome the problem of the wastewater treatment as compared with the wet processing.
The heat development recording device is mainly constructed of a conveyor for conveying a heat development recording material after forming a latent image, a heating section corresponding to the heat development section, and a cooling section for cooling the heat development recording material having been heat developed in the heating section. The heating section is constructed by aligning a plural number of heating units having a heat plate and plural press rolls aligned therein along the conveyance direction of the heat development recording material. The heat development recording material is held between the heat plate and the press rolls, heated at a development temperature while being conveyed, and then transported into the cooling section. The cooling section is constructed of a plural number of roll pairs and cools the developed heat development recording material to approximately room temperature at a prescribed cooling rate.
According to the thus constructed heat development recording device, the development is smoothly and surely carried out without causing an abrupt temperature change (an abrupt temperature reduction) in the heat development recording material, thereby preventing uneven development, generation of a wrinkle caused by an abrupt temperature reduction and a lowering of the image quality from occurring.
In addition to the above-described heat development recording device, JP-A-9-307767 relates to the present invention.
The density of a photosensitive material at the time of heat development rises with an increase of the heat development temperature. Accordingly, in order to obtain a stable density, it is necessary to precisely control the heat development temperature and the time from substantial start to completion of the development (substantial heat development time). On the other hand, a heat development recording device is required to have readiness of rise temperature and temperature stability even at the time of first start-up of the device on a day. However, in usual PID control or on-off control, though the temperature of a site in the vicinity of a heater becomes stable fast, the temperature response of sites far from the heater becomes slow due to heat conduction, heat capacity, heat dissipation, etc. For example, if recording is carried out immediately after start-up of the device and before the heat development section has not been sufficiently warmed yet, there is caused a phenomenon in which the density is lowered. This is because even if the heater reaches the target temperature, the press rolls, etc. in the surroundings thereof are not sufficiently warmed yet. For this reason, even if the heater temperature has reached the target temperature after start-up of the device, it is necessary to make the device in the recordable state after the elapse of a certain time. However, since the temperature of the press rolls, etc. depends upon the operation history of the device, it was difficult to specify a waiting time. Also, it may be considered to set up the heater temperature immediately after the start-up high. However, even in this case, since the temperature depends upon the operation history of the device, it was difficult to specify to what extent the temperature should be raised.
That is, in the case where the heat development recording device is considered as a heat storage medium, its accumulated heat quantity changes by the operation history, and the temperature of sites far from the temperature sensor is affected by the varied heat accumulation temperature. Therefore, it was difficult to precisely control the temperature in the heat development section.
On the other hand, it may be considered to align a number of temperature sensors. However, not only the device became complicated, but also a load of the control processing increased, resulting in a delay of the development processing time. Also, it may be considered to correct the exposure amount through a variety of correction processing, thereby coping with a reduction of the density. However, even in this case, a load of the control processing increased, resulting in a delay of the development processing time. Further, it may be considered to construct a device provided with a stabilized very large heat storage medium as heating means. However, if the heat development recording device is constructed such that it is provided with such a heat storage medium, not only the whole of the device becomes large, but also the device costs become high. On the other hand, if it fails to precisely control the heat development temperature, a stable density was not obtained, resulting in generating a reduction of the image quality such as occurrence of uneven density.